Size reduction of complementary metal-oxide-semiconductor (CMOS) devices, such as transistors, has enabled the continued improvement in speed, performance, density, and cost per unit function of integrated circuits over the past few decades. As sizes are reduced, there has been a trend to integrate more functions on a single chip, some of which require higher voltage levels. The use of higher voltages with shorter gate length MOSFETs, however, may create undesirable effects, such as punch-through.
Generally, punch-through occurs when an electrical connection is formed between different regions during high-voltage operation, possibly creating a short condition between the two regions causing the device to fail. One attempt to solve this problem utilizes a barrier layer formed along a surface of a substrate. An epitaxial layer is grown on the substrate, and a transistor having high-voltage wells in the source/drain regions is then formed in the epitaxial layer.
This process, however, is time-consuming, expensive, and generally requires additional process steps. For example, the epitaxial layer is a time-consuming process and reduces the amount of units that may be produced within a given amount of time. Additionally, the high-voltage wells are different than the low-voltage wells used in other areas of the wafer. Accordingly, particularly in designs in which it is desirable to utilize low-voltage and high-voltage devices on a single substrate, high-voltage devices typically require additional processing steps and longer processing times.
Accordingly, there is a need for high-voltage devices that may be fabricated easily and cost-effectively, particularly in conjunction with low-voltage devices.